28 Loss of Heat from Bare Steam Pipes 



We have then a simple means of accurately estimating the 



loss of heat from a steam pipe or boiler. 



I am at a loss to explain why the experiments require the 



value of /fto be .87 when Pclet's experiments point to a value 



of .64. It may have been because his tests were made with very 



much smaller differences of temperature. 



The effect of the condition of the surface of the pipe may be 



inferred from the following values found by Peclet : 



Ordinary sheet iron , . .567 



Rusty sheet iron 688 



New cast iron 650 



Rusty cast iron 688 



The effect of air currents is very marked in the case of bare 



pipes. Mr. Norton in his experiments found that the draft from 



an electric fan increased the loss by one -half in the case of a 



vertical 4 -inch pipe. 



Mr. Barrus showed conclusively by several tests that the 



loss of heat from a bare pipe is the same whether the steam 



therein is at rest or in motion at ordinary velocity. 



